1. Field of the Invention
The present invention relates to a communication system, constructed by interconnecting a plurality of repeaters, each connected to at least one node terminal, by a data transmission line, for exchanging data between node terminals, between repeaters or between a node terminal and a repeater. Particularly, it relates to a communication method which can satisfy a request for transmitting emergency data immediately without executing a redundant processing procedure and without producing a transmission wait time when a node terminal connected to a certain repeater makes the request to transmit emergency data including an emergency command informing the occurrence of an emergency to at least one node terminal connected to another repeater quickly and to a communication system.
2. Prior Art
Heretofore, there has been generally known a communication system, constructed by interconnecting a plurality of repeaters, each connected to at least one node terminal, by a data transmission line, for exchanging data between node terminals, between repeaters or between a node terminal and a repeater.
In the above conventional communication system, when a node terminal connected to a certain repeater is to transmit communication data to at least one node terminal connected to another repeater, the node terminal having communication data to be transmitted monitors whether the data transmission line is used by another node terminal before it transmits the communication data and transmits the communication data to the above predetermined destination node terminal when the line can be used. On the other hand, when the line cannot be used, the node terminal waits until the line can be used and transmits the communication data to the predetermined destination node terminal when the line can be used.
As another prior art, when the line cannot be used as the result of monitoring the usage state of the line, the node terminal waits for a random time interval and tries to transmit communication data to the predetermined destination node terminal after the end of the wait time.
Thereby, communication data can be transmitted to the predetermined destination node terminal without fail by preventing as much as possible the destruction of the communication data caused by the collision of data which occurs when a plurality of different node terminals try to transmit communication data at the same time.
In the above conventional communication system, there is a case where a node terminal connected to a certain repeater makes a request to transmit emergency data including an emergency command informing the occurrence of an emergency to at least one node terminal connected to another repeater quickly.
In this case, the node terminal having the emergency data tries to forcedly transmit the emergency data to the predetermined destination node terminal irrespective of the result of monitoring the usage state of the line and to transmit the emergency data again after data being communicated is destroyed by this forced transmission.
However, according to an emergency handling method in the above conventional communication system, a redundant processing procedure must be executed that the transmission of emergency data is tried again after the data being communicated is destroyed by the forced transmission of emergency data, whereby it takes relatively long time to secure a usable communication line with the result that it is difficult to transmit emergency data to a destination node terminal quickly.
In view of the above situation, it is an object of the present invention to provide a communication method and a communication system which can satisfy a request for transmitting emergency data immediately without executing a redundant processing procedure and without producing a unnecessary wait time when a node terminal connected to a certain repeater yields the request to transmit emergency data including an emergency command informing the occurrence of an emergency to at least one node terminal connected to another repeater quickly.
To attain the above object of the present invention, there is provided a communication method, used in a communication system consisting of a plurality of repeaters interconnecting by a data transmission line, and each connected to at least one node terminal, exchanging data between node terminals, between repeaters, or between a node terminal and a repeater, the communication method comprising the steps of, at each of a plurality of repeaters: upon receiving the emergency data including an emergency command informing the occurrence of an emergency from a node terminal connected to own repeater, a repeater other than own repeater, or a node terminal connected to a repeater other than own repeater, temporarily suspending a processing of inputting and outputting communication data which is not emergency data for own repeater; preferentially permitting a processing of inputting and outputting emergency data for own repeater; and transmitting the received emergency data to at least one destination on the data transmission line.
According to the present invention, each of the plurality of repeaters temporarily suspends the processing of inputting and outputting communication data which is not emergency data for own repeater, preferentially permits the processing of inputting and outputting emergency data for the repeater and transmits the received emergency data to at least one destination when it receives the emergency data including an emergency command informing the occurrence of an emergency from a node terminal connected to own repeater, a repeater other than own repeater or a node terminal connected to a repeater other than own repeater. Therefore, for example, when a node terminal connected to a certain repeater yields a request to transmit emergency data including an emergency command to at least one node terminal connected to another repeater quickly, the request for transmitting the emergency data can be accomplished immediately without executing a redundant processing procedure and without producing unnecessary wait time.
In a preferred embodiment of the present invention, the emergency data further include emergency information on an emergency.
In a preferred embodiment of the present invention, upon receiving an emergency data including an emergency cancellation command informing the end of the emergency after the reception of the emergency data including the emergency command, each of the plurality of repeaters resumes the processing of inputting and outputting communication data which is not emergency data for own repeater and transmits emergency data including the emergency cancellation command to at least one destination on the data transmission line.
To attain the above object of the present invention, there is provided a communication system consisting of a plurality of repeaters interconnecting by a data transmission line, and each connected to at least one node terminal, for exchanging data between node terminals, between repeaters, or between a node terminal and a repeater, each of the plurality of repeaters comprising: receiving means for receiving communication data from a node terminal connected to own repeater, a repeater other than own repeater, and a node terminal connected to a repeater other than own repeater; emergency data prior processing means for temporarily suspending a processing of inputting and outputting communication data which is not emergency data for own repeater and preferentially permitting a processing of inputting and outputting emergency data for own repeater when communication data received by the receiving means is emergency data including an emergency command informing an occurrence of an emergency; and transmitting means for transmitting the communication data to at least one destination on the data transmission line, wherein the transmitting means transmits the emergency data received by the receiving means to at least one destination when the communication data received by the receiving means is the emergency data including the emergency command.
According to the present invention, in each of the plurality of repeaters, the receiving means receives communication data from a node terminal connected to own repeater, a repeater other than own repeater or a node terminal connected to a repeater other than own repeater. When the communication data received by the receiving means is emergency data including an emergency command informing the occurrence of an emergency, the emergency data prior processing means temporarily suspends the processing of inputting and outputting communication data which is not emergency data for own repeater and preferentially permits the processing of inputting and outputting emergency data for own repeater. The transmitting means transmits the emergency data including the emergency command to at least one destination when the communication data received by the receiving means is the emergency data including the emergency command.
Thereby, when a node terminal connected to a certain repeater yields a request to transmit emergency data including an emergency command to at least one node terminal connected to another repeater quickly, the request for transmitting emergency data can be accomplished immediately without executing a redundant processing procedure and without producing unnecessary wait time.
In a preferred embodiment of the present invention, the emergency data further include emergency information on an emergency.
In a preferred embodiment of the present invention, each of the plurality of repeaters further comprises resuming means for resuming the processing of inputting and outputting communication data which is not emergency data for own repeater, when communication data received by the receiving means is emergency data including an emergency cancellation command informing the end of the emergency after the reception of the emergency data including the emergency command, and the transmitting means transmits the emergency data including the emergency cancellation command to at least one destination when the communication data received by the receiving means is the emergency data including the emergency cancellation command.
The above and other objectives, features and advantages of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.